the crowds swelled to more than 30,000 thursday, president obama arrived armed with new energy and attack lines against romney that were absent from wednesday's debate. all but calling his opponent a liar. >> governor romney may dance around his positions. he may do a tap dance and a two-step, but if you want to be president, then you owe the american people the truth. >> reporter: mr. obama's top advisers concedes the president needs to come back fighting the next two debates and find a sharper way to sell his message. we'll make adjustments, his top strategist said. president obama took aim at cutting funds to pbs, the home to big bird. that's less than $100 million a year, just a fraction of the overall federal budget. >> thank goodness somebody's finally cracking down on big bird! who knew that he was responsible for all these deficits? elmo's got to watch out. >> reporter: meanwhile, a past presidential nominee, former vice president al gore, who had his own debate struggles, offered this unusual explanation for mr. obama's uninspired performance, blaming the high altitude in denver.